Potter's Choice Glazes - Layering Food Safe - Questions And Records

Hello! New potter here and I am trying to always start in the right direction and make sure everything I make is responsible and safe for anyone who I give or hopefully sell my pottery too one day. I have ordered a few of the pint sized potter's choice glazes for layering a few cups and bowls I was going to make for my own personal use. However I have been studying up on these forums and reading through all of the FAQ and I realized that just because they are AP safety rating and dinnerware safe doesn't mean once I layer them they still will be. In fact AMACO even states:

Intermixing ANY or overlapping ANY dinnerware glazes, whether leaded or lead free, will not assure that they will remain dinnerware safe. Also, additions of underglazes or oxides may alter the composition of the glaze and disrupt the formula balance thus making it unsafe for dinnerware. Only testing for lead release will determine if they are dinnerware safe.

At the time when I ordered these glazes I missed that message nicely placed at the bottom of their website under all the benefits of their safe glazes. However I did make sure I bought all AP safety rating glazes as I have a 3.5 year old around and even though hes a smart guy, you never know what kids are going to do, much less his friends.

My question is, has anyone used some combination of the potter's choice glazes that are listed here: http://www.amaco.com...-choice-glazes/ and have had them sent off for testing? Is it even possible for us to list what we have done here and be confident that we are producing safe pots for our own personal use?

And if so would we be able to use for this thread is to list glaze combinations that we have sent off for testing before we make some plates/cups/bowls for our personal household use. I was hoping that I could list the bisque firing, clay type, glazes used, # of layers, layering order, and glaze firing schedule for future people who use the same glaze choices as I have decided too.

I am almost regretting my decision to buy potters choice glazes now, because I don't feel like I can safely use them without sending each combination I have made off for testing. I don't particularly care for some the base colors of the glaze as much as I do the combination effects.

For now I am thinking I might just end up using the celebration glazes in single layers while I have some sample cups sent off for safety testing.

I know a lot of people make their own glazes and know that their combinations after making them have been safety approved. As a new potter I haven't moved on to creating my own glazes yet. Although now it seems like I need to invest in purchasing "Mastering Cone 6 Glazes", and start creating my own as soon as possible.

Hope this all makes sense, and I hope that others have had some experience with this to give me some insights into what I might be up against?

The difficulty in sending commercial glazes for testing is knowing what it is you want the lab to test. When you send a cup for testing, you ask the lab to test for leeching of cobalt carbonate or copper carbonate or manganese, etc. But, with commercial glazes, you don't know the ingredients used to make that glaze, so you don't really know what to ask the lab to test. With own made glazes, you know what is in the glaze and can ask that a specific ingredient be tested.

One would think that a company that actively encourages layering and mixing (and all of them do) would have the courtesy and ethic of also having those combinations tested. But, that is asking too much.

So, layer and overlap on the exteriors, but use only a liner glaze on the interiors that come into contact with food, drinks.

The difficulty in sending commercial glazes for testing is knowing what it is you want the lab to test. When you send a cup for testing, you ask the lab to test for leeching of cobalt carbonate or copper carbonate or manganese, etc. But, with commercial glazes, you don't know the ingredients used to make that glaze, so you don't really know what to ask the lab to test. With own made glazes, you know what is in the glaze and can ask that a specific ingredient be tested.

This is a very good point that I didn't think about at all. It would be near impossible to be sure that the food was indeed safe since you don't have any idea what went into the layering combination.

So, layer and overlap on the exteriors, but use only a liner glaze on the interiors that come into contact with food, drinks.

This is basically what I came to a conclusion about last night after I purchased the ipad version of Mastering Cone 6 Glazes. I didn't realize there was an ebook version until I started doing research, thought I was gonna have to spend 200+ dollars buying the book.

Thanks for all your help bciskepottery. Your comments have already increased my knowledge and inspired me to continue with these glazes.

I have another question about some things I have read here in this glaze forum and FAQ. A lot of people state that certain glazes are safe after covered with a thick clear. Is this the standard truth or is this only with certain glazes in particular discussions in that thread?

I have another question about some things I have read here in this glaze forum and FAQ. A lot of people state that certain glazes are safe after covered with a thick clear. Is this the standard truth or is this only with certain glazes in particular discussions in that thread?

Manufacturers' recommend underglazes be covered with a clear to make them food safe. A clear over another glaze . . . well, back to the new glaze discussion above, as you are changing the composition of the two glazes. Is there a specific thread you were reading and referring?

Grype, You definitely don't have to spend $200 on Mastering Cone 6 glazes. You can get a reprint edition for around $20. The downside, it's fully black and white. The authors have made color photos, of the glazes, available on their site. I bought the book and plan to print off the glaze color photos for reference.

And to add to the underglaze comment, many underglazes look better with the clear on top. I have a dark blue underglaze in my classroom, that looks mediocre when fired on its own. With a good coat of clear over top, it looks great.

Yea, I just purchased it for the ipad. I dont have an ipad of my own, but my wife does, so I am just gonna borrow hers to read through the book, then when she isn't using it ill constantly brush up. I got it for 19.99 in color, which i thought was an insane deal compared to the 195 on amazon. Hopefully one day I will snag it at a book sale or something in hard cover!

I definitely will have to experiment with underglazes, right now I am just doing regular cone 6 glazes of amaco brand. I wanted to layer for some cups and bowls, but my plan is just to layer the outside about a half 3/4 from the rim of the bowl or cup. This will give it almost the look I was going for while still staying dinnerware safe. I plan to eventually get some stuff sent off and tested, but for now I will just stick to what I know is safe if fired to cone 6 as directed.

I have another question about some things I have read here in this glaze forum and FAQ. A lot of people state that certain glazes are safe after covered with a thick clear. Is this the standard truth or is this only with certain glazes in particular discussions in that thread?

Absolutely and completely untrue. That assumes that the layers do not "mingle". They do.

It is not necessarily true with slips and underglazes either. SO much depends on the application relationships, and the specific glaze over the specific underglaze or slip.

This is a complex subject.

Also see the FAQ section here in "Technical".

best,

......................john

John BaymoreImmediate Past President; Potters CouncilProfessor of Ceramics; New Hampshire Insitute of Art